Architecture AR/AP Bookkeeping

Getting Paid on Time: Retainers, Phase Invoices, and Collections for Architecture Studios

Published September 21, 2026 by Invisible LLC Team · 9 min read

Your phase invoices went out. Your retainer is on file. And there's still a CD-phase invoice from June sitting in QuickBooks with a little red "overdue" tag that you've been meaning to deal with for three weeks.

You're a principal, not a collections department. Nobody went to architecture school to learn how to ask a client, politely, for the fourth time, where the money is. So most studios don't really have a collections process. They have a feeling of dread and an inbox search.

This post is about replacing the dread with a routine.

The takeaways. Most studio cash problems aren't pricing problems; they're getting-paid problems. Fix them in order: structure the retainer so it actually protects you, invoice on a fixed monthly rhythm instead of at phase end, read your AR aging every week, and run a follow-up sequence that keeps the money conversation separate from the design relationship. The contract terms that back all of this up are probably already in your agreement.

Retainers: why the standard one doesn't protect your cash

Start before the first invoice, because that's where most collection problems are baked in.

The standard AIA owner-architect agreement treats the up-front money as an initial payment. It's the minimum payment under the agreement, and it's credited to the owner's account on the final invoice (AIA Document B101–2017, §11.10.1.1). That's a sensible default. It's also why a retainer rarely feels like it helps. The money arrives on day one and does its real work at the very end of the project, sometimes a year or more later. In between, you're billing and chasing every phase exactly as you would without it.

Studios usually structure it one of three ways, and each does a different job:

Structure	How it works	What it's good for
Held to final invoice	Collected at signing, applied against the last invoice (the B101 default)	Protecting the end of the project, when the client's motivation to pay is lowest
Applied up front	Credited against the first invoice or two	Funding early schematic work; no protection later
Rolling (evergreen)	Held on account; each invoice draws on it and the client tops it back up	Keeping you ahead of the work for the whole engagement

None of these is right for every client. A rolling retainer gives you the strongest cash position and is the hardest to sell. Held-to-final is the easiest to sell and does the least for your cash month to month. Whichever you pick, pick it on purpose and write it into the agreement, instead of reusing whatever last year's proposal said.

One bookkeeping point that saves real trouble: a retainer is not income when it lands. Until you do the work it pays for, it's money you're holding for the client. It belongs in a liability account, not on your revenue line. Book it as revenue on arrival and your P&L will look great in the month you sign and mysteriously bad in the month you finish. Our studio chart of accounts template shows where it goes.

Invoice on a calendar, not on a milestone

The second collection problem is timing. An invoice that goes out late gets paid late, and nothing you do in collections gets those weeks back.

Two habits fix most of it.

Bill monthly within long phases. Phase-end billing on a fourteen-week CD phase means fourteen weeks of payroll before an invoice goes out. Monthly percent-complete billing against the phase fee is normal practice, and clients see it all the time. Our post on work in progress covers what that unbilled time costs you, and our G702/G703 billing guide covers the mechanics if your clients want the AIA forms.

Pick an invoice day and never miss it. The last business day of the month, or the first. Which one doesn't matter. What matters is that clients learn when your invoice arrives, and that the invoice never waits for someone to find a free afternoon.

Then make each invoice easy to approve. Invoices get paid late for boring reasons, and the most common one is that someone in the client's accounts payable department can't match it to anything. Every invoice should carry:

the project name, plus the client's project or PO number if they use one
the phase and the percent complete you're billing against
reimbursables itemized, with backup attached and your markup shown the way your agreement defines it
additional services listed separately, with a reference to the written authorization
the due date as an actual date, not "net 30"

If a stranger in the client's accounting department can approve the invoice without emailing you, it gets paid on time.

How to improve accounts receivable: read the aging every week

Your AR aging report lists every unpaid invoice grouped by how long it's been outstanding: current, 1–30 days past due, 31–60, 61–90, and over 90. QuickBooks produces it in two clicks. Most principals look at it quarterly, if ever.

Read it weekly, and read it for three things:

Anything that moved into a new bucket this week. That's your follow-up list. An invoice crossing from current into 1–30 gets a reminder. One crossing into 31–60 gets a phone call.
Concentration. If one client accounts for most of your 60-plus balance, you don't have a collections problem anymore. You have a client-risk problem, and a decision to make about whether to keep working while they're behind.
Disputed versus slow. An invoice that's late because the client is slow needs a reminder. One that's late because the client thinks it's wrong needs a conversation about scope, and no reminder will fix it. Tag them differently so you treat them differently.

You'll see benchmarks for "days sales outstanding," the average number of days it takes to collect. There's no universal standard for studios. It varies widely with client mix: public and institutional clients pay on their own schedules, and residential clients often pay fast or not at all. The useful comparison is your own trend. Calculate it the same way every month (AR balance divided by the last three months of billings, times 90, is a simple version) and watch whether it's getting better or worse.

A collection sequence that keeps the relationship

Studios avoid collections because it feels like a threat to the relationship. The fix is structural: keep the money conversation separate from the design conversation. Your project architect should never be the one asking about the invoice. Neither should you, until it's serious.

Here's an example sequence. Adjust the days to your own terms and clients. What matters is that it exists, it's written down, and someone other than the principal runs the first four steps.

When	What	Who
Invoice day	Invoice sent, backup attached	Bookkeeper or office manager
A few days before due	Friendly heads-up: "Invoice 1042 is due Friday. Let us know if you need anything to process it."	Bookkeeper
1 day past due	Short reminder with the invoice re-attached	Bookkeeper
About 15 days past due	Call to the client's AP contact: is it approved, is anything missing, when will it run?	Bookkeeper
About 30 days past due	Principal-to-principal (or principal-to-owner) call. Not a threat, just a check on whether something's wrong	Principal
About 45 days past due	Written notice referencing the agreement's payment terms	Principal
Beyond that	Formal remedies (below)	Principal and attorney

The early steps sound almost too gentle. That's deliberate. Most late payments aren't hostile. They're an invoice stuck in someone's approval queue, and a polite reminder clears them without anyone feeling chased.

The contract terms that back you up

When the gentle steps don't work, your agreement is what gives the later ones weight. Know what's in yours before you need it.

If you use the standard B101, the 2017 edition includes two terms that matter here. Check your own version, because many studios and owners modify them.

Payment is due on invoice, and overdue amounts can carry interest. §11.10.2 leaves blanks for how many days after the invoice date interest starts, and at what rate. Leave them blank and you've given up the easiest lever you had. Fill them in.
Nonpayment counts as substantial nonperformance. Under §9.1, the owner's failure to pay is cause for termination or, at your option, suspension of services on seven days' written notice. The AIA Trust has a useful practitioner summary. You'll rarely use it, but knowing you can, and mentioning it calmly at the 45-day step, changes the tone of the conversation.

Beyond the contract, many states give design professionals lien rights on the property they helped improve. Illinois' Mechanics Lien Act, for example, expressly covers services performed as an architect (770 ILCS 60/1). Lien deadlines are short and courts enforce the technical requirements strictly, so if a balance is heading that way, talk to a construction attorney early, not at the deadline.

Very few studio collection problems should get this far. The ones that do are almost always the ones where the studio kept working for months while the balance grew.

What to fix before your next agreement goes out

Five changes, in order of how much cash they pull forward:

Choose the retainer structure on purpose, and write down how and when it's applied.
Add monthly billing within phases to your standard terms.
Fill in the interest blanks in §11.10.2, or whatever your agreement's equivalent is.
Define reimbursable markup and backup requirements, so reimbursables stop being the line clients question.
Require written authorization before additional services, so every change becomes something you can invoice.

Then build the weekly habit: read the aging, move each bucket one step forward, and let someone other than you make the first calls.

Where this fits

Invoicing and payment tracking is where most of our studio relationships start. It's the part principals most want off their plate, and it's the part that pulls cash forward fastest. Our receivables and payables work covers everything above: invoices out on schedule with backup attached, a weekly aging review, and follow-up that doesn't route through the principal. If you're working out who should own the rest of the back office, our guide to bookkeeping for architects lays out what a studio bookkeeper should handle. And project margin versus firm margin covers what to do with the numbers once they're current.

You can see how we work with architecture and design practices, or request a quote and we'll go through your current aging report with you. One report, one conversation, and an honest read on where your cash is stuck.