Copy-paste templates for the monthly check
https://archon-partners.com/guides/project-cost-vs-budget/

From Archon & Partners. Replace everything in [square brackets], read each one, and use it from your own accounts. Check your agreement before mentioning interest, suspension or any contract term. This is not legal or tax advice.

=== 1. Sheet layout and formulas ===
When: Set up once. One row per project, refreshed after each monthly close.
Subject: Columns A to I, data from row 2

A Project | B Budget | C Cost to date | D % complete (as 0.40) | E Planned cost | F Variance | G Estimate at completion | H Status | I Decision

E2  =B2*D2
F2  =C2-E2
G2  =IF(D2>0, C2/D2, "")
H2  =IF(D2=0, "", IF(F2>B2*0.05, "Over", IF(F2<-B2*0.05, "Under", "On track")))

The 5% band in H2 is our suggestion. Set your own and keep it the same every month.

=== 2. Monthly request to project leads ===
When: The first working day after the month closes.
Subject: Percent complete for [month], by [date]

Hi [name],

For the monthly cost check, could you send percent complete for each active phase on your projects by [date]?

[Project]: [phase] [%], [phase] [%]
[Project]: [phase] [%]

Please base it on the deliverables list, not hours spent. If something has changed in scope or the client has asked for extra work, note it here too.

Thank you,
[your name]

=== 3. Decision note for a project over budget ===
When: In the project file, the same week a project is flagged.
Subject: [Project]: cost check [month]

Budget: [budget]
Percent complete: [%]
Cost to date: [cost], planned [planned cost], variance [variance]
Estimate at completion: [estimate] (an estimate, based on cost to date)

Cause: [scope added without a change / late client information / more senior staff than planned / consultant added / other]
Decision: [raise a scope change / change staffing / fee conversation with client / accept and record]
Owner: [name]  By: [date]
Review again: [next month]