How retainers work

The rate a retainer does not state

A retainer agreement names two things: a fee and, usually, the hours it covers. Divide one by the other and you get the rate the arrangement implies — 2,000 a month for up to 20 hours is 100 an hour. That figure is what the fee was priced on, and it is the last time anybody works it out.

What you actually earned is the fee divided by the hours you actually worked. Do 20 and the two match. Do 30 and the same 2,000 is 66.67 an hour, a third less, without a conversation, a renegotiation or anything that looks like a pay cut from the outside.

Why the quiet months do not cancel the busy ones

The usual defence of an overrun is that it evens out — a heavy month is paid for by a light one. Sometimes that is true. It is worth checking rather than assuming, because the two are not symmetrical: an overrun has no ceiling and an underrun does. You can work 40 hours on a 20-hour retainer, but you cannot work less than nothing, so the most a quiet month can give back is the 20 hours it was worth.

Run a few real months through the calculator rather than the one you remember. The month you remember is usually the bad one.

An overage rate is what stops the drift

An agreement with a rate for hours beyond the included ones holds its value: the extra work is charged by the hour, the effective rate stays near the implied one, and neither side has to raise it as a problem. Without one, every hour past the limit is free, and the retainer calculator says how many of them there were.

That is arithmetic, not a recommendation. Plenty of retainers are deliberately loose, and a client who never overruns is worth keeping on generous terms. The figure is only useful if you know it.

Unused hours belong to your contract, not to the arithmetic

If you worked fewer hours than the retainer covers, the calculator counts what was left and stops there. Whether unused hours roll into next month, expire at the end of it, or were never meant to be tracked at all is a question the agreement answers. Some retainers buy availability rather than output, and a quiet month on one of those is the arrangement working.