Are there any cautions or common mistakes in creating summary reports with data drawn from more than one table?

I'm trying to pull data from two related tables, but am getting invalid totals as well as display oddities (blank lines and multiple total lines in GrandSmry part where there shoud only be one). I started with a manually-constructed report and also tried the report wizard. Neither work right. I'm doing something wrong, but I don't know what.

To be more specific, I have one table which records data from a checkbook, with a related table that contains data for those checks which are payroll checks and have withholding amounts. (Most checks don't have this info, so I put it in a separate table so there aren't blank fields/excess data in records for which withholding is irrelevant, otherwise with auto entry calcs, etc, there would be extraneous (& false) data in all the records.) I'm now trying to create a summary report that gives totals of amounts withheld, using a summary field (Ttl) for each data field (e.g., fedWH > smryFedWH) in a Trailing Grand Summary part.

You might want to consider another design. Put all your checks in one table and use a sub-table (a one to one relationship) to hold the extra data.

A 1-to-1 rel. is what this is in actuality, I just don't have the rel. defined right (the graph shows "crows feet" on what should be the "sub table." To change that I assume I make a field in the sub-table unique?

I'll do some experimenting tomorrow night (no time until then). Sounds simple enough; if I can't figure it out, I'll be back. Thanks for your help.